Fragment synthesis of substituted cyclic peptides

ABSTRACT

There is described herein use of a compound of formula (I) below to make cyclic peptides.

RELATED APPLICATION

This application is a national phase application under 35 U.S.C. § 371 of International Application No. PCT/CA2016/000275 filed Nov. 14, 2016, which claims priority from U.S. Provisional Application No. 62/254,003 filed on Nov. 11, 2015, both of which are incorporated herein by reference in their entirety.

FIELD

The present invention relates to cyclic amino acid molecules and methods of preparing the same.

BACKGROUND

Peptides play vital roles by mediating a wide range of biological processes, acting as hormones, antibiotics, and signaling molecules. Due to the highly specific interaction with their biological targets, peptides have been widely used in medicine. However, the enormous therapeutic potential of peptides is not always easy to realize due to their low bioavailability. This shortcoming is a consequence of the degradation of peptides by endo- and exopeptididases, which results in poor in vivo stability of peptides. Compared to their linear counterparts, cyclic peptides are more resistant to degradation. There are two main reasons for this stability. Firstly, exopeptidases cannot cleave the cyclic peptide at its (non-existent) ends. Secondly, cyclic peptides, especially those with a small-to-medium ring size, are protected against endopeptidases because the constrained cyclic peptide backbone prevents the adaptation of the required extended conformation during proteolysis. In addition, the reduced charge and intramolecular hydrogen bonding within cyclic peptides facilitate passive membrane permeability, which contributes to their enhanced bioavailability. Most significantly, conformational constraints imposed on the amino acid sequence by the cyclic topology maximize enthalpic interactions between cyclic peptides and their biochemical targets while ensuring favourable entropy of binding.

SUMMARY OF THE INVENTION

In an aspect, there is provided a compound of formula (I):

wherein R¹, R², R^(3′) R⁴, R⁵ and R⁶ are each independently selected from the group consisting of a protecting group; H; lower alkyl; aryl; heteroaryl; alkenyl; heterocycle; acids of the formula —C(O)OH; esters of the formula —C(O)OR* wherein R* is selected from alkyl and aryl; amides of the formula —C(O)NR**R***, wherein R** and R*** are independently selected from H, alkyl and aryl; —CH2C(O)R, wherein R is selected from —OH, lower alkyl, aryl, -loweralkyl-aryl, or —NRaRb, where Ra and Rb are independently selected from H, lower alkyl, aryl or -loweralkyl-aryl; —C(O)Rc, wherein Rc is selected from lower alkyl, aryl or -lower alkyl-aryl; or -lower alkyl-ORd, wherein Rd is a suitable protecting group or OH group; all of which are optionally substituted at one or more substitutable positions with one or more suitable substituents; provided that R³ or R⁴ can be covalently linked to R¹ or R² to form a cyclic secondary amine, and/or to R⁵ or R⁶ to form a ring; R³ and R⁴ may be covalently linked to each other to form a ring; and R⁵ and R⁶ may be covalently bound to each other to form a ring;

-   R⁷ is H, a protecting group, lower alkyl, benzyl, alkenyl, lower     alkyloxy; aryl; heteroaryl; heterocycle; —C(O)R****, wherein R****     is independently selected from alkyl, aryl, heteroaryl, amino,     aminoalkyl, aminoaryl, aminoheteroaryl, alkoxy, aryloxy,     heteroaryloxy; —CH₂C(O)R; —C(O)Rc; all of which are optionally     substituted at one or more substitutable positions with one or more     suitable substituents or along with R⁸ or R⁹, a cyclic side chain of     a proteinogenic or a non-proteinogenic amino acid having, the     N-terminus thereof being the N—R⁷, wherein the proteinogenic or a     non-proteinogenic amino acid can be substituted with a suitable     substituent;     R⁸ and R⁹ are independently selected from the amino acid side chains     of a proteinogenic or a non-proteinogenic amino acid having, the     N-terminus thereof being the N—R⁷, or may form a cyclic side chain     with R⁷; and     R¹⁶ is H, a protecting group, a resin, lower alkyl, allyl,     tert-butyl, or benzyl;     stereocentres 1*, 2* and 3* are each independently selected from R     and S; and     n is 1, 2, 3, or 4 and where n is 2-4, each R⁸ and each R⁹ are     independent of each other.

In an aspect, there is provided a method of preparing the compound of the invention, comprising reacting

with

and an isocyanide; wherein R⁵ or R⁶ is a carboxamide.

In an aspect, there is provided a method of preparing the compound of formula (II),

comprising binding at least one amino acid to the compound of the invention (Formula (I)) using protecting group based peptide synthesis and performing a head-to-tail cyclization; wherein Z is an amino terminus of an amino acid; —C═O— adjacent L is the carboxy terminus of an amino acid; and Z along with L and —C═O— is a proteogenic or non-proteogenic amino acid or peptide or peptidomimetic

In an aspect, there is provided a method of preparing the compound of formula (III),

comprising performing a head-to-tail cyclization on the compound of the invention; wherein R¹, R³, R⁴, R⁵ and R⁶ are each independently selected from the group consisting of H; lower alkyl; aryl; heteroaryl; alkenyl; heterocycle; acids of the formula —C(O)OH; esters of the formula —C(O)OR* wherein R* is selected from alkyl and aryl; amides of the formula —C(O)NR**R***, wherein R** and R*** are independently selected from H, alkyl and aryl; —CH₂C(O)R, wherein R is selected from —OH, lower alkyl, aryl, -loweralkyl-aryl, or —NRaRb, where Ra and Rb are independently selected from H, lower alkyl, aryl or -loweralkyl-aryl; —C(O)Rc, wherein Rc is selected from lower alkyl, aryl or -lower alkyl-aryl; or -lower alkyl-ORd, wherein Rd is a suitable protecting group or OH group; all of which are optionally substituted at one or more substitutable positions with one or more suitable substituents; provided that R³ or R⁴ can be covalently linked to R¹ to form a cyclic secondary amine, and/or to R⁵ or R⁶ to form a ring; R³ and R⁴ may be covalently linked to each other to form a ring; and R⁵ and R⁶ may be covalently bound to each other to form a ring; stereocentres 1* and 2* and 3* are independently selected from R and S; and Z-L-C═O is an amino acid.

In an aspect, there is provided a compound of formula (II)

wherein R¹, R², R³, R⁴, R⁵ and R⁶ are each independently selected from the group consisting of a protecting group; H; lower alkyl; aryl; heteroaryl; alkenyl; heterocycle; acids of the formula —C(O)OH; esters of the formula —C(O)OR* wherein R* is selected from alkyl and aryl; amides of the formula —C(O)NR**R***, wherein R** and R*** are independently selected from H, alkyl and aryl; —CH₂C(O)R, wherein R is selected from —OH, lower alkyl, aryl, -loweralkyl-aryl, or —NRaRb, where Ra and Rb are independently selected from H, lower alkyl, aryl or -loweralkyl-aryl; —C(O)Rc, wherein Rc is selected from lower alkyl, aryl or -lower alkyl-aryl; or -lower alkyl-ORd, wherein Rd is a suitable protecting group or OH group; all of which are optionally substituted at one or more substitutable positions with one or more suitable substituents; provided that R³ or R⁴ can be covalently linked to R¹ or R² to form a cyclic secondary amine, and/or to R⁵ or R⁶ to form a ring; R³ and R⁴ may be covalently bound to each other to form a ring; and R⁵ and R⁶ may be covalently bound to each other to form a ring;

-   R⁷ is H, a protecting group, lower alkyl, benzyl, alkenyl, lower     alkyloxy; aryl; heteroaryl; heterocycle; —C(O)R****, wherein R****     is independently selected from alkyl, aryl, heteroaryl, amino,     aminoalkyl, aminoaryl, aminoheteroaryl, alkoxy, aryloxy,     heteroaryloxy; —CH₂C(O)R; —C(O)Rc; all of which are optionally     substituted at one or more substitutable positions with one or more     suitable substituents;     -   or, along with R⁸ or R⁹, a cyclic side chain of a proteinogenic         or a non-proteinogenic alpha-amino acid having, the N-terminus         thereof being the N—R⁷;         R⁸ and R⁹ are independently selected, from the amino acid side         chains of a proteinogenic or a non-proteinogenic alpha-amino         acid having, the N-terminus thereof being the N—R⁷, or may form         a cyclic side chain with R⁷;         stereocentres 1*, 2* and 3* are each independently selected from         R and S;         wherein Z is an amino terminus of an amino acid; —C═O— adjacent         L is the carboxy terminus of an amino acid; and Z along with L         and —C═O— is a proteogenic or non-proteogenic amino acid or         peptide or peptidomimetic; and         n is 1, 2, 3, or 4 and where n is 2-4, each R⁸ and each R⁹ are         independent of each other.

In an aspect, there is provided a compound of formula (III),

wherein R¹, R³, R⁴, R⁵ and R⁶ are each independently selected from the group consisting of H; lower alkyl; aryl; heteroaryl; alkenyl; heterocycle; acids of the formula —C(O)OH; esters of the formula —C(O)OR* wherein R* is selected from alkyl and aryl; amides of the formula —C(O)NR**R***, wherein R** and R*** are independently selected from H, alkyl and aryl; —CH₂C(O)R, wherein R is selected from —OH, lower alkyl, aryl, -loweralkyl-aryl, or —NRaRb, where Ra and Rb are independently selected from H, lower alkyl, aryl or -loweralkyl-aryl; —C(O)Rc, wherein Rc is selected from lower alkyl, aryl or -lower alkyl-aryl; or -lower alkyl-ORd, wherein Rd is a suitable protecting group or OH group; all of which are optionally substituted at one or more substitutable positions with one or more suitable substituents;

-   -   provided that R³ or R⁴ can be covalently linked to R¹ to form a         cyclic secondary amine, and/or to R⁵ or R⁶ to form a ring; R³         and R⁴ may be covalently bound to each other to form a ring; and         R⁵ and R⁶ may be covalently bound to each other to form a ring;         stereocentres 1* and 2* and 3* are independently selected from R         and S; and         Z-L-C═O is an amino acid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is an HPLC trace of an Ugi reaction conducted at 0° C. in dichloromethane and methanol with no Bronsted or Lewis acid.

FIG. 1b is an HPLC trace of an Ugi reaction conducted at 0° C. in dichloromethane and methanol with no Bronsted or Lewis acid.

FIG. 2a is a LC trace of an Ugi reaction conducted at 10° C. in dichloromethane and methanol in the presence of 10 mol % of an acid such as diphenyl phosphate.

FIG. 2b is a LC trace of an Ugi reaction conducted at 10° C. in dichloromethane and methanol in the presence of 10 mol % of an acid such as diphenyl phosphate.

DETAILED DESCRIPTION

In an aspect, there is provided a compound of formula (I):

wherein R¹, R², R³, R⁴, R⁵ and R⁶ are each independently selected from the group consisting of a protecting group; H; lower alkyl; aryl; heteroaryl; alkenyl; heterocycle; acids of the formula —C(O)OH; esters of the formula —C(O)OR* wherein R* is selected from alkyl and aryl; amides of the formula —C(O)NR**R***, wherein R** and R*** are independently selected from H, alkyl and aryl; —CH₂C(O)R, wherein R is selected from —OH, lower alkyl, aryl, -loweralkyl-aryl, or —NRaRb, where Ra and Rb are independently selected from H, lower alkyl, aryl or -loweralkyl-aryl; —C(O)Rc, wherein Rc is selected from lower alkyl, aryl or -lower alkyl-aryl; or -lower alkyl-ORd, wherein Rd is a suitable protecting group or OH group; all of which are optionally substituted at one or more substitutable positions with one or more suitable substituents; provided that R³ or R⁴ can be covalently linked to R¹ or R² to form a cyclic secondary amine, and/or to R⁵ or R⁶ to form a ring; R³ and R⁴ may be covalently linked to each other to form a ring; and R⁵ and R⁶ may be covalently bound to each other to form a ring;

-   R⁷ is H, a protecting group, lower alkyl, benzyl, alkenyl, lower     alkyloxy; aryl; heteroaryl; heterocycle; —C(O)R****, wherein R****     is independently selected from alkyl, aryl, heteroaryl, amino,     aminoalkyl, aminoaryl, aminoheteroaryl, alkoxy, aryloxy,     heteroaryloxy; —CH₂C(O)R; —C(O)Rc; all of which are optionally     substituted at one or more substitutable positions with one or more     suitable substituents     -   or along with R⁸ or R⁹; a cyclic side chain of a proteinogenic         or a non-proteinogenic amino acid having, the N-terminus thereof         being the N—R⁷, wherein the proteinogenic or a non-proteinogenic         amino acid can be substituted with a suitable substituent;         R⁸ and R⁹ are independently selected from the amino acid side         chains of a proteinogenic or a non-proteinogenic amino acid         having, the N-terminus thereof being the N—R⁷, or may form a         cyclic side chain with R⁷; and         R¹⁰ is H, a protecting group, a resin, lower alkyl, allyl,         tert-butyl, or benzyl;         stereocentres 1*, 2* and 3* are each independently selected from         R and S; and         n is 1, 2, 3, or 4 and where n is 2-4, each R⁸ and each R⁹ are         independent of each other.

A protecting group or protective group is a substituent introduced into a molecule to obtain chemoselectivity in a subsequent chemical reaction. Many protecting groups are known in the art and a skilled person would understand the kinds of protecting groups that would be incorporated and could be used in connection with the methods described herein. In “protecting group based peptide synthesis”, typically solid phase peptide synthesis, the desired peptide is prepared by the step-wise addition of amino acid moieties to a building peptide chain. The two most widely used protocols, in solid-phase synthesis, employ tert-butyloxycarbonyl (Boc) or 9-fluorenylmethoxycarbonyl (Fmoc) as amino protecting groups. Amino protecting groups generally protect an amino group against undesirable reactions during synthetic procedures and which can later be removed to reveal the amine. Commonly used amino protecting groups are disclosed in Greene, T. W. et al., Protective Groups in Organic Synthesis, 3rd Edition, John Wiley & Sons (1999). Amino protecting groups include acyl groups such as formyl, acetyl, propionyl, pivaloyl, t-butylacetyl, 2-chloroacetyl, 2-bromoacetyl, trifluoroacetyl, trichloroacetyl, o-nitrophenoxyacetyl, .alpha.-chlorobutyryl, benzoyl, 4-chlorobenzoyl, 4-bromobenzoyl, 4-nitrobenzoyl, and the like; sulfonyl groups such as benzenesulfonyl, p-toluenesulfonyl and the like; alkoxy- or aryloxy-carbonyl groups (which form urethanes with the protected amine) such as benzyloxycarbonyl (Cbz), p-chlorobenzyloxycarbonyl, p-methoxybenzyloxycarbonyl, p-nitrobenzyloxycarbonyl, 2-nitrobenzyloxycarbonyl, p-bromobenzyloxycarbonyl, 3,4-dimethoxybenzyloxycarbonyl, 3,5-dimethoxybenzyloxycarbonyl, 2,4-dimethoxybenzyloxycarbonyl; 4-methoxybenzyloxycarbonyl, 2-nitro-4,5-dimethoxybenzyloxycarbonyl; 3,4,5-trimethoxybenzyloxycarbonyl, 1-(p-biphenylyl)-1-methylethoxycarbonyl, .alpha.-,.alpha.-dimethyl-3,5-dimethoxybenzyloxycarbonyl, benzhydryloxycarbonyl, t-butyloxycarbonyl (Boc), diisopropylmethoxycarbonyl, isopropyloxycarbonyl, ethoxycarbonyl, methoxycarbonyl, allyloxycarbonyl (Alloc), 2,2,2-trichloroethoxycarbonyl, 2-trimethylsilylethyloxycarbonyl (Teoc), phenoxycarbonyl, 4-nitrophenoxycarbonyl, fluorenyl-9-methoxycarbonyl (Fmoc), cyclopentyloxycarbonyl, adamantyloxycarbonyl, cyclohexyloxycarbonyl, phenylthiocarbonyl and the like; aralkyl groups such as benzyl, triphenylmethyl, benzyloxymethyl and the like; and silyl groups such as trimethylsilyl and the like. Amine protecting groups also include cyclic amino protecting groups such as phthaloyl and dithiosuccinimidyl, which incorporate the amino nitrogen into a heterocycle. Typically, amino protecting groups include formyl, acetyl, benzoyl, pivaloyl, t-butylacetyl, phenylsulfonyl, Alloc, Teoc, benzyl, Fmoc, Boc and Cbz. It is well within the skill of the ordinary artisan to select and use the appropriate amino protecting group for the synthetic task at hand.

As used, herein, the term “amino acid” refers to molecules containing an amine group, a carboxylic acid group and a side chain that varies. Amino acid is meant to include not only the twenty amino acids commonly found in proteins but also non-standard amino acids and unnatural amino acid derivatives known to those of skill in the art, and therefore includes, but is not limited to, alpha, beta and gamma amino acids. Peptides are polymers of at least two amino acids and may include standard, non-standard, and unnatural amino acids.

The term “suitable substituent” as used in the context of the present invention is meant to include independently H; hydroxyl; cyano; alkyl, such as lower alkyl, such as methyl, ethyl, propyl, n-butyl, t-butyl, hexyl and the like; alkoxy, such as lower alkoxy such as methoxy, ethoxy, and the like; aryloxy, such as phenoxy and the like; vinyl; alkenyl, such as hexenyl and the like; alkynyl; formyl; haloalkyl, such as lower haloalkyl which includes CF₃, CCl₃ and the like; halide; aryl, such as phenyl and napthyl; heteroaryl, such as thienyl and furanyl and the like; amide such as C(O)NR_(a)R_(b), where R_(a) and R_(b) are independently selected from lower alkyl, aryl or benzyl, and the like; acyl, such as C(O)—C₆H₅, and the like; ester such as —C(O)OCH₃ the like; ethers and thioethers, such as O-Bn and the like; thioalkoxy; phosphino; and —NR_(a)R_(b), where R_(a) and R_(b) are independently selected from lower alkyl, aryl or benzyl, and the like. It is to be understood that a suitable substituent as used in the context of the present invention is meant to denote a substituent that does not interfere with the formation of the desired product by the processes of the present invention.

As used in the context of the present invention, the term “lower alkyl” as used herein either alone or in combination with another substituent means acyclic, straight or branched chain alkyl substituent containing from one to six carbons and includes for example, methyl, ethyl, 1-methylethyl, 1-methylpropyl, 2-methylpropyl, and the like. A similar use of the term is to be understood for “lower alkoxy”, “lower thioalkyl”, “lower alkenyl” and the like in respect of the number of carbon atoms. For example, “lower alkoxy” as used herein includes methoxy, ethoxy, t-butoxy.

The term “alkyl” encompasses lower alkyl, and also includes alkyl groups having more than six carbon atoms, such as, for example, acyclic, straight or branched chain alkyl substituents having seven to ten carbon atoms.

The term “aryl” as used herein, either alone or in combination with another substituent, means an aromatic monocyclic system or an aromatic polycyclic system. For example, the term “aryl” includes a phenyl or a napthyl ring, and may also include larger aromatic polycyclic systems, such as fluorescent (eg. anthracene) or radioactive labels and their derivatives.

The term “heteroaryl” as used herein, either alone or in combination with another substituent means a 5, 6, or 7-membered unsaturated heterocycle containing from one to 4 heteroatoms selected from nitrogen, oxygen, and sulphur and which form an aromatic system. The term “heteroaryl” also includes a polycyclic aromatic system comprising a 5, 6, or 7-membered unsaturated heterocycle containing from one to 4 heteroatoms selected from nitrogen, oxygen, and sulphur.

The term “cycloalkyl” as used herein, either alone or in combination with another substituent, means a cycloalkyl substituent that includes for example, but is not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and cycloheptyl.

The term “cycloalkyl-alkyl-” as used herein means an alkyl radical to which a cycloalkyl radical is directly linked; and includes, but is not limited to, cyclopropylmethyl, cyclobutylmethyl, cyclopentyl methyl, 1-cyclopentylethyl, 2-cyclopentylethyl, cyclohexylmethyl, 1-cyclohexylethyl and 2-cyclohexylethyl. A similar use of the “alkyl” or “lower alkyl” terms is to be understood for aryl-alkyl-, aryl-loweralkyl- (eg. benzyl), -lower alkyl-alkenyl (eg. allyl), heteroaryl-alkyl-, and the like as used herein. For example, the term “aryl-alkyl-” means an alkyl radical, to which an aryl is bonded. Examples of aryl-alkyl- include, but are not limited to, benzyl (phenylmethyl), 1-phenylethyl, 2-phenylethyl and phenylpropyl.

As used herein, the term “heterocycle”, either alone or in combination with another radical, means a monovalent radical derived by removal of a hydrogen from a three- to seven-membered saturated or unsaturated (including aromatic) cyclic compound containing from one to four heteroatoms selected from nitrogen, oxygen and sulfur. Examples of such heterocycles include, but are not limited to, aziridine, epoxide, azetidine, pyrrolidine, tetra-hydrofuran, thiazolidine, pyrrole, thiophene, hydantoin, diazepine, imidazole, isoxazole, thiazole, tetrazole, piperidine, piperazine, homopiperidine, homopiperazine, 1,4-dioxane, 4-morpholine, 4-thiomorpholine, pyridine, pyridine-N-oxide or pyrimidine, and the like.

The term “alkenyl”, as used herein, either alone or in combination with another radical, is intended to mean an unsaturated, acyclic straight chain radical containing two or more carbon atoms, at least two of which are bonded to each other by a double bond. Examples of such radicals include, but are not limited to, ethenyl (vinyl), 1-propenyl, 2-propenyl, and 1-butenyl.

The term “alkynyl”, as used herein is intended to mean an unsaturated, acyclic straight chain radical containing two or more carbon atoms, at least two of which are bonded to each other by a triple bond. Examples of such radicals include, but are not limited to, ethynyl, 1-propynyl, 2-propynyl, and 1-butynyl.

The term “alkoxy” as used herein, either alone or in combination with another radical, means the radical —O—(C_(1-n))alkyl wherein alkyl is as defined above containing 1 or more carbon atoms, and includes for example methoxy, ethoxy, propoxy, 1-methylethoxy, butoxy and 1,1-dimethylethoxy. Where n is 1 to 6, the term “lower alkoxy” applies, as noted above, whereas the term “alkoxy” encompasses “lower alkoxy” as well as alkoxy groups where n is greater than 6 (for example, n=7 to 10). The term “aryloxy” as used herein alone or in combination with another radical means —O-aryl, wherein aryl is defined as noted above.

A peptide is a polymer of two or more amino acids.

In some embodiments, one and only one of R¹ and R² is a protecting group.

In some embodiments, R¹ and R² are both H.

In some embodiments, R³ and R⁴ are each independently selected from the group consisting of amino acid chains of a proteinogenic or a non-proteinogenic alpha-amino acids, preferably CH₃, H, isobutyl, and —CH₂—S—R*****, wherein R***** is selected from lower alkyl; lower amino alkyl; aryl; heteroaryl; alkenyl; or heterocycle; all of which are optionally substituted at one or more substitutable positions with one or more suitable substituents; preferably R***** is phenyl or phenyl substituted with lower alkyl, halogen, or lower amino alkyl. In some embodiments, the proteinogenic or non-proteinogenic alpha-amino acid is a primary amino acid. In some embodiments, the proteinogenic or non-proteinogenic alpha-amino acid is a secondary amino acid, preferably proline.

In some embodiments, R⁵ and R⁶ are either (i) H and a carboxamide, the carboxamide preferably being —C(O)NH-tert-butyl; or (ii) H and H respectively.

In some embodiments, R⁷ and either R⁸ or R⁹ are selected to form proline, the N-terminus thereof being the N—R⁷.

In some embodiments, R¹⁰ is selected from the group consisting of CH₃ and H.

In some embodiments, none of R¹, R², R³, R⁴, R⁵ and R⁶ are an acid of the formula —C(O)OH.

In some embodiments, R⁷ is H, a protecting group, lower alkyl, benzyl, or alkenyl.

In an aspect, there is provided a method of preparing the compound of the invention, comprising reacting

with

and an isocyanide; wherein R⁵ or R⁶ is a carboxamide.

In some embodiments, this method is performed in the presence of at least one of:

In an aspect, there is provided a method of preparing the compound of formula (II),

comprising binding at least one amino acid to the compound of the invention (Formula (I)) using protecting group based peptide synthesis and performing a head-to-tail cyclization; wherein Z is an amino terminus of an amino acid; —C═O— adjacent L is the carboxy terminus of an amino acid; and Z along with L and —C═O— is a proteogenic or non-proteogenic amino acid or peptide or peptidomimetic

In some embodiments, the peptide is bound to the compound of Formula (I).

In some embodiments, the peptide is 2-8 amino acids in length.

In some embodiments, two or more fragment compounds described herein are bound to each other using the protecting group based peptide synthesis.

In an aspect, there is provided a method of preparing the compound of formula (III),

comprising performing a head-to-tail cyclization on the compound of the invention; wherein R¹, R³, R⁴, R⁵ and R⁶ are each independently selected from the group consisting of H; lower alkyl; aryl; heteroaryl; alkenyl; heterocycle; acids of the formula —C(O)OH; esters of the formula —C(O)OR* wherein R* is selected from alkyl and aryl; amides of the formula —C(O)NR**R***, wherein R** and R*** are independently selected from H, alkyl and aryl; —CH₂C(O)R, wherein R is selected from —OH, lower alkyl, aryl, -loweralkyl-aryl, or —NRaRb, where Ra and Rb are independently selected from H, lower alkyl, aryl or -loweralkyl-aryl; —C(O)Rc, wherein Rc is selected from lower alkyl, aryl or -lower alkyl-aryl; or -lower alkyl-ORd, wherein Rd is a suitable protecting group or OH group; all of which are optionally substituted at one or more substitutable positions with one or more suitable substituents; provided that R³ or R⁴ can be covalently linked to R¹ to form a cyclic secondary amine, and/or to R⁵ or R⁶ to form a ring; R³ and R⁴ may be covalently linked to each other to form a ring; and R⁵ and R⁶ may be covalently bound to each other to form a ring; stereocentres 1* and 2* and 3* are independently selected from R and S; and Z-L-C═O is an amino acid.

In some embodiments of the methods of preparing the compound of formulas (II) and (III), the protecting group based peptide synthesis is performed on solid phase. In some embodiments, the fragment compound described herein is bound to the solid phase.

In an aspect, there is provided a compound of formula (II)

wherein R¹, R², R³, R⁴, R⁵ and R⁶ are each independently selected from the group consisting of a protecting group; H; lower alkyl; aryl; heteroaryl; alkenyl; heterocycle; acids of the formula —C(O)OH; esters of the formula —C(O)OR* wherein R* is selected from alkyl and aryl; amides of the formula —C(O)NR**R***, wherein R** and R*** are independently selected from H, alkyl and aryl; —CH₂C(O)R, wherein R is selected from —OH, lower alkyl, aryl, -loweralkyl-aryl, or —NRaRb, where Ra and Rb are independently selected from H, lower alkyl, aryl or -loweralkyl-aryl; —C(O)Rc, wherein Rc is selected from lower alkyl, aryl or -lower alkyl-aryl; or -lower alkyl-ORd, wherein Rd is a suitable protecting group or OH group; all of which are optionally substituted at one or more substitutable positions with one or more suitable substituents; provided that R³ or R⁴ can be covalently linked to R¹ or R² to form a cyclic secondary amine, and/or to R⁵ or R⁶ to form a ring; R³ and R⁴ may be covalently bound to each other to form a ring; and R⁵ and R⁶ may be covalently bound to each other to form a ring;

-   R⁷ is H, a protecting group, lower alkyl, benzyl, alkenyl, lower     alkyloxy; aryl; heteroaryl; heterocycle; —C(O)R****, wherein R****     is independently selected from alkyl, aryl, heteroaryl, amino,     aminoalkyl, aminoaryl, aminoheteroaryl, alkoxy, aryloxy,     heteroaryloxy; —CH₂C(O)R; —C(O)Rc; all of which are optionally     substituted at one or more substitutable positions with one or more     suitable substituents     -   or, along with R⁸ or R⁹, a cyclic side chain of a proteinogenic         or a non-proteinogenic alpha-amino acid having, the N-terminus         thereof being the N—R⁷;         R⁸ and R⁹ are independently selected from the amino acid side         chains of a proteinogenic or a non-proteinogenic alpha-amino         acid having, the N-terminus thereof being the N—R⁷, or may form         a cyclic side chain with R⁷;         stereocentres 1*, 2* and 3* are each independently selected from         R and S;         wherein Z is an amino terminus of an amino acid; —C═O— adjacent         L is the carboxy terminus of an amino acid; and Z along with L         and —C═O— is a proteogenic or non-proteogenic amino acid or         peptide or peptidomimetic; and         n is 1, 2, 3, or 4 and where n is 2-4, each R⁸ and each R⁹ are         independent of each other.

In an aspect, there is provided a compound of formula (III),

wherein R¹, R³, R⁴, R⁵ and R⁶ are each independently selected from the group consisting of H; lower alkyl; aryl; heteroaryl; alkenyl; heterocycle; acids of the formula —C(O)OH; esters of the formula —C(O)OR* wherein R* is selected from alkyl and aryl; amides of the formula —C(O)NR**R***, wherein R** and R*** are independently selected from H, alkyl and aryl; —CH₂C(O)R, wherein R is selected from —OH, lower alkyl, aryl, -loweralkyl-aryl, or —NRaRb, where Ra and Rb are independently selected from H, lower alkyl, aryl or -loweralkyl-aryl; —C(O)Rc, wherein Rc is selected from lower alkyl, aryl or -lower alkyl-aryl; or -lower alkyl-ORd, wherein Rd is a suitable protecting group or OH group; all of which are optionally substituted at one or more substitutable positions with one or more suitable substituents;

-   -   provided that R³ or R⁴ can be covalently linked to R¹ to form a         cyclic secondary amine, and/or to R⁵ or R⁶ to form a ring; R³         and R⁴ may be covalently bound to each other to form a ring; and         R⁵ and R⁶ may be covalently bound to each other to form a ring;         stereocentres 1* and 2* and 3* are independently selected from R         and S; and         Z-L-C═O is an amino acid.

The following examples are illustrative of various aspects of the invention, and do not limit the broad aspects of the invention as disclosed herein.

Examples

Preparation of Fragments—Generic Synthetic Scheme

For instances where R³, R⁴, R⁵ and R⁶=H

R⁵ and R⁶=H but one of R³ or R⁴≠H, a further scheme was employed.

Preparation of Fragments

Reaction Molarity: 0.15 M

A mixture of Fmoc-L-Ala-OH (9.6 g, 30.7 mmol), N,O-dimethylhydroxylamine.HCl (3.6 g, 36.8 mmol), and HCTU (15.24 g, 36.8 mmol) in CH₂Cl₂ (200 mL), was cooled to 0° C. DIPEA (16.04 mL, 92.1 mmol) was then slowly added to the stirring mixture. The cooling bath was removed and the reaction was stirred at room temperature (rt) for 16 h. A 10% solution of HCl (100 mL) was added resulting in the formation of a precipitate, which was removed through filtration. The filtrate was washed with 10% HCl (3×100 mL) and brine (2×100 mL). The organic phase was then dried over Na₂SO₄. The solvent was removed under reduced pressure to give crude Compound 1 (10.5 g, 29.6 mmol, 97% yield), which was used in the next reaction without purification.

Reaction Molarity: 0.12 M

Lithium aluminum hydride powder (3.5 g, 92.1 mmol) was placed in a dry, 1 L flask. THF (Sigma-Aldrich, 250 ppm of BHT, ACS reagent >99.0%, 200 mL) was added, and the resulting slurry was cooled to −78° C., with stirring. To the slurry was added a solution of the crude Compound 1 (30 g; effective quantity estimated to be 21.7 g, 61.4 mmol) in THF (300 mL). The reaction vessel was transferred to an ice/water bath, and maintained at 0° C. for 1 h. To the reaction at 0° C., was added dropwise acetone (50 mL), then H₂O (5 mL) and then the reaction was left to stir for an additional hour at rt. The mixture was filtered through Celite, washed with EtOAc (300 mL) and MeOH (300 mL), and the filtrate was concentrated. The crude material was dissolved in CHCl₃ (200 mL) and washed with brine (2×100 mL) and the organic phase was then dried over Na₂SO₄, filtered and concentrated to give Compound 2 as a white solid, 13.0 g (44 mmol, 72% yield for two steps).

Reaction Molarity: 0.055 M

Ugi reaction: to a solution of Compound 2 (13.0 g, 44.0 mmol) in MeOH (400 mL) and CH₂Cl₂ (200 mL) was added tert-butyl isocyanide (5 mL, 44.0 mmol) and diphenyl phosphate (1.1 g, 4.4 mmol). The reaction was then cooled to 0° C. and a solution of H-L-Pro-OH (5.06 g, 44.0 mmol) in MeOH (200 mL) was added dropwise over 5 h. The temperature was then warmed up to rt and the reaction was left to stir overnight. LC-MS analysis showed that the reaction was complete, and a mixture of diastereomers had formed. The solvent was evaporated, and the crude material was filtered over silica gel using a solution of 50% EtOAc/Hexane as an eluent. The solution was concentrated to give a mixture of Compound 3A, having S,S,S-stereochemistry across stereocentres 1*, 2* and 3* [see Formula (I) and Formula (II)] and Compound 3B, having S,R,S-stereochemistry across stereocentres 1*, 2* and 3* [see Formula (I) and Formula (II)]. The mixture was a white-yellow solid (17.2 g, 78%).

A further consideration to the synthesis of Compounds 3A and 3B, and related analogs, is the practical outcome in terms of the balance between the desired chemical entities and potential side-products. For example, when the Ugi reaction is conducted at 0° C. in DCM and MeOH solvents with no Bronsted or Lewis acid, the following HPLC traces of the crude reaction mixture were obtained (FIG. 1a, FIG. 1b).

In contrast, when 10 mol % of an acid such as diphenyl phosphate is added to the reaction in these solvents at 0° C., the following LC traces were obtained (FIG. 2a, FIG. 2b).

The acid-mediated Ugi reaction produces a cleaner crude profile trace than the Ugi reaction conducted in the absence of an acid.

Reaction Molarity: 0.295 M

To the crude mixture of Compound 3A and Compound 3B (17.2 g, 34 mmol) in dioxane (300 mL) was added 25% HCl (16 mL) at ambient temperature. The mixture was stirred at 100° C. for 36 h. LC-MS analysis showed that the reaction was complete. The solvent was concentrated under reduced pressure and the solid-oil was dissolved in CH₂Cl₂ (20 mL) and diluted with a solution of 50% EtOAc/Hexane (200 mL), the formed solid was filtered over Celite and then washed with MeOH. The MeOH was evaporated and the solid residue. (14.8 g, 88% yield of crude) was purified via reverse-phase silica chromatography. CombiFlash conditions of 28%-40% MeCN (containing 0.1% formic acid) in water (containing 0.1% formic acid) were employed to separate the diastereomers and afforded Compound 4A, a fragment with S,S,S-stereochemistry (9.45 g, 56% yield) and Compound 4B, a fragment with S,R,S-stereochemistry (1.0 g, 6% yield. The 50% EtOAc/Hexane filtrate was also later concentrated under reduced pressure to reveal an additional 3.75 g of a crude mixture of Compounds 4A and 4B.

Reaction Molarity: 0.0385 M

To a mixture of Fmoc-L-prolinal (10 g, 33.8 mmol) in allyl alcohol (80 mL) and CH₂Cl₂ (800 mL) was added tert-butyl isocyanide (3.82 mL, 33.8 mmol) and diphenyl phosphate (845 mg, 3.38 mmol). Then H-L-Nva-OH (3.96 g, 33.8 mmol) was added and the suspension was stirred for two days until the solid disappeared. LC-MS analysis showed that the reaction was complete, and a mixture of diastereomers, Compounds 4C and 4D, had formed. The solvent was evaporated, and the crude was filtered over silica gel using AcOEt as an eluent. The solution was concentrated to give a white-yellow solid (18.6 g, >99%).

To the crude 4C and 4D diastereomer mixture (3.22 g, 6.0 mmol) in dry CH₂Cl₂ (75 mL) and under N₂ atmosphere, was added Pd(PPh₃)₄ (347 mg, 0.3 mmol) and PhSiH₃ (2.21 mL, 18.0 mmol). After 30 minutes, the reaction turned red/brown in color. LC-MS analysis showed that the reaction was complete after 1 h. MeOH (100 mL) was added to the flask and the mixture was stirred for an additional 30 minutes. The solvent was evaporated, and the crude material was filtered over charcoal using AcOEt as an eluent. The solvent was removed and the crude material was purified via reverse-phase silica chromatography. CombiFlash purification conditions: 36-40% MeCN (containing 0.1% formic acid) in water (containing 0.1% formic acid). The fractions were concentrated giving diastereomer 4E (780 mg, 26%) and diastereomer 4F (350 mg, 12%).

Reaction Molarity: 0.046 M

To a mixture of Fmoc-L-Gln(Trt)-H (34.25 g, 57.61 mmol; prepared via LiAlH₄-mediated reduction of the corresponding Weinreb amide derivative of Fmoc-L-Gln(Trt)-OH, analogous to the two-step transformation of Fmoc-L-Ala-OH to Compounds 1 and 2) in CH₂Cl₂ (1250 mL) was added tert-butyl isocyanide (6.49 mL, 57.61 mmol) and phenylphosphinic acid (2.0 g, 14.32 mmol). Then H-L-Pro-O^(t)Bu (9.05 mL, 57.61 mmol) was added and the reaction was stirred overnight. LC-MS analysis (after treatment with TFA) showed that the reaction was complete. The solvent was evaporated, the crude material was diluted with a solution of TFA/CH₂Cl₂ (1:1, 200 mL), and the mixture was stirred for 24 h. LC-MS analysis showed that the reaction was complete, and a mixture of diastereomers had formed. The solvent was removed and the crude material was purified via reverse-phase silica chromatography. CombiFlash purification conditions: 25-35% MeCN (containing 0.1% formic acid) in water (containing 0.1% formic acid). The fractions were concentrated giving diastereomer 4G (4.1 g, 9.5%) and diastereomer 4H (5.9 g, 13.5%).

Reaction Molarity: 0.25 M

To a mixture of Boc-L-prolinal (100 mg, 0.5 mmol) and H-L-Pro-OBn.HCl (121 mg, 0.5 mmol) in CH₂Cl₂ (2 mL) was added tert-butyl isocyanide (0.057 mL, 0.5 mmol) and the reaction was stirred overnight. LC-MS analysis showed that the reaction was complete (ratio 83:17, desired product:side product). The solvent was removed and the crude material was purified via reverse-phase silica chromatography. CombiFlash purification conditions: 40-55% MeCN (containing 0.1% formic acid) in water (containing 0.1% formic acid). The solution was concentrated to give Compound 41 as a white solid (86.1 mg, 35%).

To a solution of Fmoc-L-prolinal (5.0 g, 16.95 mmol) in a mixture of THF (250 mL) and H₂O (10 mL) at 0° C. were added KCN (1.1 g, 16.95 mmol) and H-L-Pro-O^(t)Bu.HCl (3.5, 16.95 mmol). The reaction was stirred overnight at room temperature and monitored by LC-MS. Then, the solvent was evaporated and the crude material was dissolved in AcOEt (250 mL). The organic phase was washed with brine (3×100 mL), dried over Na₂SO₄, filtered and evaporated. The crude was then dissolved in CH₂Cl₂ and filtered over silica gel. The solution was concentrated to give Compound 4J a white-yellow oil (5.5 g, 60%).

To a solution of Fmoc-L-prolinal (5.0 g, 16.95 mmol) in a mixture of CH₂Cl₂ (250 mL) and H₂O (10 mL) at 0° C. were added KCN (1.1 g, 16.95 mmol) and H-L-Pro-OBn.HCl (4.09, 16.95 mmol). The reaction was stirred overnight at room temperature and monitored by LC-MS. Then, the solvent was quenched with HCl (10%, 100 mL) and the mixture was extracted with CH₂Cl₂ (3×100 mL). The organic phase was dried over Na₂SO₄, filtered and evaporated. The solution was concentrated to give Compound 4K a white-yellow oil (6.5 g, 70%).

A suspension of the nitrile 4K (1.0 g, 1.96 mmol) in a 10% solution of AcOH in HCl conc. (15 mL) and H₂O (10 mL) was placed in a sealed tube and refluxed at 70° C. for 2 days. The reaction was monitored by LC-MS. Then, the solid was filtered and washed with CH₂Cl₂. The solvent was removed and the crude material was purified via reverse-phase silica chromatography. CombiFlash purification conditions: 35-55% MeCN (containing 0.1% formic acid) in water (containing 0.1% formic acid). The solution was concentrated to give Compound 4L as a white solid (368 mg, 43%).

To a solution of Fmoc-I-alaninal (3.3 g, 11.1 mmol; Compound 2) in dry CH₂Cl₂ (50 mL) under inert atmosphere at 0° C. were added H-L-Pro-OBn.HCl (2.7 g, 11.1 mmol) and tris(trimethylsiloxy)ethylene (4.3 mL, 13.3 mmol). The reaction was placed in the fridge over the weekend at −20° C. and monitored by LC-MS. The solvent was removed and the crude material was purified via reverse-phase silica chromatography. CombiFlash purification conditions: 35-55% MeCN (containing 0.1% formic acid) in water (containing 0.1% formic acid). The solution was concentrated to give Compound 4M as a white solid (3.3 g, 52%).

Alternatively, the initial use of a tert-butoxycarbonyl group to protect the amino terminus (N-Boc) of an amino acid provides complementary access to preparative quantities of fragments, as documented below.

Reaction Molarity: 0.255 molar

To the mixture of Boc-L-Ala-OH (5.8 g, 30.7 mmol), N,O-dimethylhydroxylamine.HCl (3.59 g, 36.8 mmol), EDC.HCl (7.05 g, 36.8 mmol), 1H-benzo[d][1,2,3]triazol-1-ol.H₂O (5.63 g, 36.8 mmol) in DCM (120 mL), was slowly added DIPEA (8.54 mL, 49.0 mmol) under stirring. The reaction mixture was left at rt for 16 h, then diluted with 360 mL EtOAc. The solution was washed with 0.2 N HCl (2×100 mL), sat. NaHCO₃ (2×100 mL) and brine (2×100 mL), then dried over MgSO₄. The solvent was removed under reduced pressure to give Compound 5 (6.85 g, 29.5 mmol, 96% yield), which was pure enough for the next step without purification.

Reaction Molarity: 0.210 M

Compound 5 (6.84 g, 29.4 mmol) was dissolved in THF (140 mL), cooled to −78° C., and 1 M LiAlH₄ in THF (32.4 mL, 32.4 mmol) was added dropwise. After 2 h, the temperature was raised from −78° C. to −30° C., and the reaction was quenched with 0.5 N HCl (80 mL) and EtOAc (400 mL). Phases were separated, and the organic phase was washed again with 0.1 N HCl (80 mL), sat. NaHCO₃ (80 mL), brine (80 mL), and dried over MgSO₄. NMR showed about 20% amide was not reduced. The crude oil was purified by flash chromatography and eluted with 20-40% EtOAc in Hexanes to give Compound 6 (3.2 g, 18.47 mmol, 62.7% yield) as a white solid (Rf=0.58; 40% EtOAc in Hex); and then 60-100% EtOAc was used to elute the starting Weinreb amide (1.78 g was recovered, Rf=0.33).

Reaction Molarity: 0.090 molar

To a mixture of Compound 6 (3.11 g, 17.96 mmol) and H-L-Pro-OH (2.171 g, 18.85 mmol) in MeOH (200 mL) was added fed-butyl isocyanide (2.028 mL, 17.96 mmol) at rt. The reaction mixture was stirred at rt for 42 h. LC-MS analysis showed that the reaction was complete. Direct flash silica gel purification gave two diastereoisomers, Compound 7A, with S,S,S-stereochemistry (3.7 g, 9.60 mmol, 53.5% yield; Rf=0.41, 40% EtOAc in Hex) and Compound 7B, with S,R,S-stereochemistry (0.7 g, 1.816 mmol, 10.11% yield; Rf=0.46, 40% EtOAc in Hex).

Reaction Molarity: 0.156 M

To Compound 7A (3.6 g, 9.34 mmol) in THF (60 mL) and 1 M lithium chloride (14.01 mL, 14.01 mmol) was added 1 M lithium hydroxide (14.01 mL, 14.01 mmol) at 0° C. The reaction mixture was stirred at 0° C. to room temperature for 4 h. LC-MS analysis showed that the reaction was complete. The solution was acidified to pH 2 with 1 N HCl, and extracted with EtOAc (4×100 mL). The combined organic phase was washed with brine (100 mL) and dried over MgSO₄. The solvent was removed under reduced pressure to give Compound 8 with S,S,S-stereochemistry (3.5 g, 9.42 mmol, 101% yield), which was used in the next reaction without purification.

Reaction Molarity: 0.174 molar

To Compound 8 (3.5 g, 9.42 mmol) in DCM (54 mL) was added 2,2,2-trifluoroacetic acid (10.82 mL, 141 mmol) at 0° C. The reaction mixture was stirred at 0° C. to room temperature for 2 h. LC-MS analysis showed that the reaction was complete. The solvent was removed under reduced pressure to give crude Compound 9 with S,S,S-stereochemistry (2.7 g, 9.95 mmol, 106% yield), which was used in the next reaction without purification.

Reaction Molarity: 0.142 molar

To a mixture of Compound 9 (2.7 g, 9.95 mmol) and Fmoc-OSu (3.69 g, 10.95 mmol) in DCM (70 mL) was added DIPEA (3.64 mL, 20.90 mmol) at 0° C. The reaction mixture was stirred at 0° C. to room temperature for 2 h. LC-MS analysis showed that the reaction was complete. The mixture was diluted with EtOAc (300 mL), washed with 0.2 N HCl (2×80 mL) and brine (80 mL), dried and evaporated. Flash silica gel purification (20% EtOAc in Hex to 100% EtOAc, then 15% MeOH in EtOAc with 0.05% HOAc) gave Fmoc-protected Compound 4A (2.4 g, 4.86 mmol, 48.9% yield; Rf=0.25, 10% MeOH in DCM).

Note that a fully-deprotected fragment can be cyclized head-to-tail as part of a strategy to prepare piperazinones and facilitate determination of the stereochemical outcome of the Ugi reaction. The additional constraints in the resulting cyclic structure lend themselves to full structure determination by 2D NMR techniques. For example, Compound 7A when treated with an acid to remove the N-Boc protecting group, can then be treated with a base to mediate cyclization by direct amidation from the free amine to the C-terminus methyl ester:

To a mixture of Compound 7 (120 mg, 0.311 mmol) in DCM (3 ml) was added 2,2,2-trifluoroacetic acid (0.596 ml, 7.78 mmol) at 0° C. The reaction mixture was stirred from 0° C. to rt for 2 h. LC-MS showed reaction is complete. The reaction mixture was concentrated to dryness and the residue was dissolved in DCM (5 ml), cooled to 0° C. 1 N sodium hydroxide (1.556 mL, 1.556 mmol) was added to pH 10. The mixture was stirred for 1 h and then extracted with DCM (3×10 mL). The combined DCM was dried over MgSO₄ and concentrated. The crude was purified by flash silica gel purification (20-100% AcOEt, then 10% MeOH in AcOEt) to give Compound 13 (55 mg, 0.217 mmol, 69.7% yield) Rf=0.45 (10% MeOH in DCM).

Preparation of Macrocycles from Fragments—Generic Synthetic Scheme

The above generic scheme depicts head-to-tail cyclization from an amino terminus of an amino acid (Z) onto the C-terminus carboxylic acid of the fragment.

Preparation of Macrocycles from Fragments—Synthetic Scheme

Preparation of Macrocycles from Fragment—General Experimental Protocol Fmoc-Fragment Amino Acid Loading onto 2-CI Trt Resin

An Fmoc-protected fragment such as Compound 4A (1.1 eq. respective to resin) was dissolved in DCM (10 mL/g of resin). The 2-chlorotrityl resin was allowed to swell in DCM (5 mL/g of resin) for 15 minutes. The DCM was then drained and the Fmoc-fragment amino acid solution was added to the vessel containing the 2-CI Trt resin. 2 eq. (respective to the amino acid) of DIPEA was added and the vessel was agitated for 5 minutes. Another 2 eq. of DI PEA was then added and the vessel was left to agitate for an additional 90 minutes. The resin was then treated with methanol (1 mL/g of resin) to endcap any remaining reactive 2-CI Trt groups. The solution was mixed for 15 minutes, drained and then rinsed with DCM (×3), DMF (×3), DCM (×2) and MeOH (×3). The resin was then dried under vacuum and weighed to determine the loading of the Fmoc-protected fragment onto the resin.

Peptide Synthesis

Fully protected resin-bound peptides were synthesized via standard Fmoc solid-phase peptide chemistry manually or using an automated peptide synthesizer. All N-Fmoc amino acids were employed. Fmoc removal was achieved by treatment with 20% piperidine in NMP twice, for 5 and 10 minutes respectively, with consecutive DMF and NMP washes after each addition. For all Fmoc amino acid couplings, the resin was treated with 3 eq. of Fmoc amino acid, 3 eq. of HATU and 6 eq. of DIPEA in NMP or DMF for 60 minutes. For difficult couplings, a second treatment with 3 eq. of Fmoc amino acid, 3 eq. of HATU and 6 eq. of DIPEA in NMP for 40 minutes was employed. Once the peptide was synthesized, following Fmoc removal, the resin was treated with 1:3, HFIP:DCM, twice for 30 minutes each, to afford cleavage from the solid support. The solvent was then removed, followed by trituration with tert-butyl methyl ether to give the linear peptide. The purity was then analyzed by reversed-phase HPLC-MS.

Cyclization

In a two-dram vial, 0.1 mmol of the linear peptide and DEPBT (1.5 eq.) were dissolved in 5 mL of freshly distilled THF (0.02 M). DIPEA (3 eq.) was then added and the reaction mixture was left to stir overnight at room temperature (16 h). Tetraalkylammonium carbonate resin (6 eq.) was then added to the reaction mixture and stirring was continued for an additional 24 h. The reaction was then filtered through a solid phase extraction vessel and rinsed with DCM (2 mL). Alternatively, after macrocyclization, a 7 M solution of ammonia in methanol (Sigma-Aldrich; 10 eq.) was added and stirring was continued for an additional 24 h. The reaction was then filtered through a solid phase extraction vessel and rinsed with DCM. The filtrate and washes were combined and the solvent was removed under reduced pressure. Deprotection of the side chain protecting groups was achieved by dissolving the peptides in 2 mL of a cleavage cocktail consisting of TFA:H₂O:triisopropylsilane (95:2.5:2.5) for two hours. Subsequently, the cleavage mixture was evaporated under reduced pressure and the peptides were precipitated twice from diethyl ether/hexanes. Peptide macrocycles were then purified by reversed-phase Flash chromatography and lyophilized.

Supporting Data

Compound 1:

¹H NMR (500 MHz, Chloroform-d) δ 7.76 (ddt, J=7.6, 1.2, 0.7 Hz, 2H), 7.64-7.58 (m, 2H), 7.39 (ttd, J=7.5, 1.1, 0.6 Hz, 2H), 7.31 (tdd, J=7.4, 2.1, 1.2 Hz, 2H), 5.67 (d, J=8.4 Hz, 1H), 4.76 (t, J=7.4 Hz, 1H), 4.43-4.30 (m, 2H), 4.22 (t, J=7.3 Hz, 1H), 3.77 (s, 3H), 3.22 (s, 3H), 1.37 (d, J=6.8 Hz, 3H); MW: 354.41 g/mol; LC-MS m/z: 355.2

Compound 2:

¹H NMR (500 MHz, Chloroform-d) δ 9.56 (s, 1H), 7.77 (d, J=7.5 Hz, 2H), 7.60 (d, J=8.0 Hz, 2H), 7.45-7.39 (m, 2H), 7.33-7.29 (m, 2H), 5.41 (d, J=4.2 Hz, 1H), 4.50-4.39 (m, 2H), 4.32 (p, J=7.2 Hz, 1H), 4.23 (t, J=6.8 Hz, 1H), 1.38 (d, J=7.3 Hz, 3H); MW: 295.3 g/mol

Compound 7A:

¹H NMR (400 MHz, Chloroform-d) δ 6.43 (s, 1H), 5.59 (br s, 1H), 4.05-3.90 (m, 1H), 3.83 (dd, J=9.0, 2.7 Hz, 1H), 3.67 (s, 3H), 3.18 (d, J=4.3 Hz, 1H), 3.00-2.92 (m, 2H), 2.23-2.03 (m, 1H), 1.91-1.77 (m, 3H), 1.41 (s, 9H), 1.32 (s, 9H), 1.22 (d, J=6.8 Hz, 3H); MW: 385.5 g/mol; LC-MS m/z: 386.3

Compound 7B:

¹H NMR (400 MHz, Chloroform-d) δ 7.13 (s, 1H), 5.53 (d, J=9.2 Hz, 1H), 4.07-3.90 (m, 1H), 3.69 (s, 3H), 3.60-3.52 (m, 1H), 3.14 (d, J=4.0 Hz, 1H), 3.01 (ddd, J=9.3, 6.3, 3.7 Hz, 1H), 2.81 (td, J=8.8, 6.5 Hz, 1H), 2.07 (dtd, J=12.6, 10.2, 9.8, 7.7 Hz, 1H), 1.93-1.75 (m, 3H), 1.40 (s, 9H), 1.31 (s, 9H), 1.15 (d, J=6.6 Hz, 3H); MW: 385.5 g/mol; LC-MS m/z: 386.3

Compound 10:

MW: 427.58 g/mol; LC-MS m/z: 428.3

Compound 3A:

MW: 507.6 g/mol; LC-MS m/z: 508.2

Compound 3B:

MW: 507.6 g/mol; LC-MS m/z: 508.2

Compound 8:

MW: 371.5 g/mol; LC-MS m/z: 372.3

Compound 11:

MW: 413.55 g/mol; LC-MS m/z: 414.3

Compound 9:

MW: 271.4 g/mol; LC-MS m/z: 272.3

Compound 4A:

¹H NMR (700 MHz, DMSO-d₆) δ 12.23 (s, 1H), 7.88 (dt, J=7.6, 0.8 Hz, 2H), 7.68-7.63 (m, 2H), 7.41 (ddt, J=8.5, 7.5, 0.8 Hz, 2H), 7.33-7.28 (m, 2H), 7.20 (s, 1H), 6.85 (d, J=8.6 Hz, 1H), 4.30-4.23 (m, 2H), 4.19 (t, J=6.9 Hz, 1H), 3.81 (ddt, J=15.2, 8.5, 6.4 Hz, 1H), 3.44 (dd, J=8.8, 5.1 Hz, 1H), 3.24 (d, J=8.6 Hz, 1H), 3.20-3.15 (m, 1H), 2.86 (td, J=7.9, 4.0 Hz, 1H), 1.95 (dq, J=12.4, 8.3 Hz, 1H), 1.77 (ddt, J=12.7, 8.2, 4.9 Hz, 1H), 1.72-1.61 (m, 2H), 1.20 (s, 9H), 1.11 (d, J=6.6 Hz, 3H). ¹³C NMR (126 MHz, DMSO-d₆) δ 175.54, 170.30, 155.51, 144.28, 141.13, 128.00, 127.99, 127.43, 127.42, 125.50, 120.51, 66.12, 65.74, 62.84, 50.77, 47.40, 47.20, 47.13, 29.69, 28.72, 23.87, 19.36; MW: 493.6 g/mol; LC-MS m/z: 494.2

Compound 12:

MW: 535.67 g/mol; LC-MS m/z: 536.3

Compound 4B:

¹H NMR (700 MHz, DMSO-d₆) δ 12.14 (s, 1H), 7.88 (dt, J=7.5, 0.9 Hz, 2H), 7.70 (s, 1H), 7.65 (d, J=7.5 Hz, 2H), 7.43-7.39 (m, 2H), 7.32 (td, J=7.4, 1.1 Hz, 2H), 6.85 (d, J=8.2 Hz, 1H), 4.33 (dd, J=10.4, 6.9 Hz, 1H), 4.28-4.18 (m, 2H), 3.87-3.78 (m, 2H), 3.25 (d, J=6.3 Hz, 1H), 2.93 (td, J=8.0, 3.7 Hz, 1H), 2.72 (q, J=7.8 Hz, 1H), 2.00-1.92 (m, 1H), 1.79 (ddt, J=12.5, 7.5, 2.7 Hz, 1H), 1.75-1.65 (m, 2H), 1.24 (s, 9H), 1.06 (d, J=6.6 Hz, 3H). ¹³C NMR (126 MHz, DMSO-d₆) δ 176.60, 170.97, 155.51, 144.34, 144.30, 141.20, 141.18, 128.07, 127.51, 125.57, 125.50, 120.60, 120.58, 120.50, 66.61, 65.77, 60.96, 50.82, 50.79, 47.38, 47.22, 30.36, 28.74, 23.95, 19.10; MW: 493.6 g/mol; LC-MS m/z: 494.2

Compound 13:

¹H NMR (400 MHz, Benzene-d₆) δ 6.50 (s, 1H), 6.03 (s, 1H), 3.27 (pd, J=6.9, 1.9 Hz, 1H), 2.90-2.77 (m, 2H), 2.68 (t, J=8.3 Hz, 1H), 2.17 (dddd, J=12.9, 11.0, 9.0, 6.9 Hz, 1H), 1.91 (q, J=8.7 Hz, 1H), 1.83-1.72 (m, 1H), 1.50 (ddtd, J=12.7, 11.0, 8.3, 4.2 Hz, 1H), 1.41-1.26 (m, 1H), 1.24 (s, 9H), 1.07 (d, J=6.8 Hz, 3H); MW: 253.4 g/mol; LC-MS m/z: 254.3

Compound 14:

¹H NMR (400 MHz, Benzene-d₆) δ 7.98 (s, 1H), 6.78 (s, 1H), 3.46 (t, J=7.7 Hz, 1H), 3.22 (dqd, J=9.2, 6.5, 1.6 Hz, 1H), 2.72-2.64 (m, 2H), 2.31-2.16 (m, 2H), 1.91 (dtd, J=12.3, 8.2, 3.8 Hz, 1H), 1.49-1.39 (m, 1H), 1.37 (d, J=6.5 Hz, 3H), 1.34-1.27 (m, 1H), 1.25 (s, 9H); MW: 253.4 g/mol; LC-MS m/z: 254.3

Compound 15:

¹H NMR (500 MHz, DMSO-d₆) δ 7.88 (dt, J=7.7, 1.0 Hz, 2H), 7.69 (dd, J=8.0, 2.9 Hz, 2H), 7.44-7.38 (m, 2H), 7.33 (tt, J=7.4, 1.3 Hz, 2H), 7.26 (d, J=8.1 Hz, 1H), 4.27 (dtd, J=40.9, 13.7, 12.1, 7.2 Hz, 3H), 3.66 (p, J=6.9 Hz, 1H), 3.33 (dd, J=14.1, 5.5 Hz, 1H), 3.25-3.19 (m, 1H), 2.78 (dd, J=12.3, 7.4 Hz, 1H), 2.64 (dd, J=12.2, 6.5 Hz, 1H), 2.57 (q, J=8.4 Hz, 1H), 2.03 (dq, J=12.7, 8.5 Hz, 1H), 1.87-1.65 (m, 3H), 1.08 (d, J=6.5 Hz, 3H); MW: 394.5 g/mol; LC-MS m/z: 395.2

Compound 16:

¹H NMR (500 MHz, DMSO-d₆) δ 8.21 (s, 1H), 7.91-7.86 (m, 2H), 7.71-7.66 (m, 2H), 7.41 (tt, J=7.5, 1.5 Hz, 2H), 7.32 (ddt, J=7.4, 5.9, 1.2 Hz, 2H), 7.17 (t, J=5.7 Hz, 1H), 4.32-4.18 (m, 3H), 3.75-3.69 (m, 1H), 3.42 (dd, J=8.6, 5.4 Hz, 1H), 3.38-3.31 (m, 1H), 3.24 (dt, J=15.2, 7.8 Hz, 1H), 2.79-2.69 (m, 1H), 1.98-1.89 (m, 1H), 1.77 (td, J=8.4, 7.9, 3.5 Hz, 1H), 1.72-1.56 (m, 3H), 1.24 (d, J=4.1 Hz, 9H); MW: 479.6 g/mol; LC-MS m/z: 480.2

Compound 17:

¹H NMR (500 MHz, DMSO-d₆) δ 7.89 (ddt, J=7.5, 1.2, 0.6 Hz, 2H), 7.72 (s, 1H), 7.71-7.66 (m, 2H), 7.41 (tdd, J=6.9, 1.2, 0.6 Hz, 2H), 7.36-7.29 (m, 3H), 4.31-4.17 (m, 3H), 3.55 (dd, J=9.4, 4.1 Hz, 1H), 3.41 (t, J=7.1 Hz, 1H), 3.29-3.18 (m, 1H), 3.01 (t, J=8.7 Hz, 1H), 2.90 (q, J=8.3 Hz, 1H), 2.03-1.91 (m, 1H), 1.83 (tt, J=7.6, 3.8 Hz, 1H), 1.75-1.55 (m, 2H), 1.24 (s, 9H); MW: 479.6 g/mol; LC-MS m/z: 480.2

Compound 18:

¹H NMR (500 MHz, Chloroform-d) δ 7.89 (dt, J=7.5, 0.9 Hz, 2H), 7.68 (d, J=7.5 Hz, 2H), 7.41 (tdt, J=7.4, 1.1, 0.5 Hz, 2H), 7.33 (ddt, J=8.4, 7.4, 1.1 Hz, 3H), 4.33 (d, J=6.7 Hz, 2H), 4.26-4.19 (m, 1H), 3.40 (dd, J=9.2, 5.0 Hz, 1H), 3.37-3.31 (m, 1H), 3.22-3.18 (m, 2H), 2.96 (dt, J=13.5, 6.9 Hz, 1H), 2.79 (dt, J=12.3, 6.1 Hz, 1H), 2.68 (q, J=9.2 Hz, 1H), 2.09 (dq, J=12.9, 8.8 Hz, 1H), 1.85 (dtd, J=23.0, 8.2, 7.8, 4.2 Hz, 2H), 1.68 (dt, J=12.6, 8.3 Hz, 1H).

Compound 19:

MW: 354.41 g/mol; LC-MS m/z: 355.2

Compound 20:

MW: 507.6 g/mol; LC-MS m/z: 508.2

Compound 21:

MW: 507.6 g/mol; LC-MS m/z: 508.2

Compound 22:

MW: 493.6 g/mol; LC-MS m/z: 494.2

Compound 23:

¹H NMR (400 MHz, DMSO-d₆) δ 7.87 (d, J=7.5 Hz, 2H), 7.68 (s, 1H), 7.63 (d, J=7.5 Hz, 2H), 7.43-7.36 (m, 2H), 7.30 (td, J=7.5, 1.1 Hz, 2H), 6.84 (d, J=8.2 Hz, 1H), 4.35-4.16 (m, 3H), 3.81 (td, J=10.8, 9.9, 4.7 Hz, 2H), 3.22 (d, J=6.3 Hz, 1H), 2.90 (d, J=9.3 Hz, 1H), 2.70 (q, J=7.7 Hz, 1H), 2.01-1.87 (m, 1H), 1.84-1.62 (m, 3H), 1.22 (s, 9H), 1.04 (d, J=6.6 Hz, 3H); MW: 493.6 g/mol; LC-MS m/z: 494.2

Compound 24:

¹H NMR (400 MHz, Benzene-d₆) δ 6.79 (s, 1H), 6.23 (s, 1H), 3.68-3.55 (m, 1H), 3.54-3.46 (m, 1H), 3.10-3.04 (m, 1H), 2.75 (ddd, J=9.4, 6.5, 2.7 Hz, 1H), 2.24 (ddt, J=13.1, 10.5, 7.7 Hz, 1H), 2.04-1.88 (m, 2H), 1.39-1.27 (m, 2H), 1.26 (s, 9H), 0.97 (ddd, J=8.7, 5.3, 2.7 Hz, 3H).

Compound 25:

¹H NMR (400 MHz, Benzene-d₆) δ 7.85 (s, 1H), 6.12 (s, 1H), 3.97-3.79 (m, 1H), 3.19-3.08 (m, 1H), 2.82 (d, J=9.7 Hz, 1H), 2.70 (td, J=8.5, 6.0 Hz, 1H), 2.31 (td, J=8.6, 5.8 Hz, 1H), 2.17 (ddt, J=12.8, 10.0, 6.4 Hz, 1H), 1.97 (dddd, J=13.0, 9.9, 8.3, 4.9 Hz, 1H), 1.48 (dddd, J=10.0, 7.5, 6.2, 3.8 Hz, 1H), 1.42-1.33 (m, 1H), 1.30 (d, J=6.3 Hz, 3H), 1.22 (s, 9H).

Compound 26:

MW: 507.6 g/mol; LC-MS m/z: 508.2

Compound 27:

MW: 507.6 g/mol; LC-MS m/z: 508.2

Compound 28:

MW: 493.6 g/mol; LC-MS m/z: 494.2

Compound 29:

MW: 493.6 g/mol; LC-MS m/z: 494.2

Compound 30:

¹H NMR (500 MHz, DMSO-d₆) δ 8.69 (br s, 1H), 8.44-8.21 (m, 2H), 7.69 (br s, 1H), 7.61 (s, 1H), 4.38 (q, J=6.6 Hz, 1H), 4.33-4.24 (m, 1H), 4.12 (dd, J=10.0, 6.1 Hz, 1H), 4.08-3.99 (m, 1H), 3.92 (p, J=6.4 Hz, 1H), 3.62 (dd, J=17.0, 5.6 Hz, 1H), 3.20-3.12 (m, 1H), 3.06-2.95 (m, 1H), 2.54 (q, J=1.9 Hz, 0H), 2.46 (p, J=1.9 Hz, 1H), 1.99 (dq, J=11.8, 8.4 Hz, 1H), 1.81 (d, J=5.6 Hz, 1H), 1.75-1.56 (m, 2H), 1.48 (td, J=13.8, 12.5, 6.5 Hz, 2H), 1.23 (s, 9H), 1.15 (d, J=7.0 Hz, 3H), 1.01 (d, J=6.3 Hz, 3H), 0.89 (dd, J=14.2, 6.2 Hz, 6H); MW: 582.7 g/mol; LC-MS m/z: 583.4

Compound 31:

¹H NMR (700 MHz, DMSO-d₆) δ 8.86 (br s, 2H), 7.65-7.50 (m, 2H), 7.04 (d, J=8.7 Hz, 1H), 6.99 (dd, J=8.6, 6.9 Hz, 2H), 6.95 (d, J=9.1 Hz, 1H), 6.74 (s, 1H), 6.66-6.62 (m, 2H), 4.53-4.46 (m, 1H), 4.31-4.24 (m, 2H), 4.20 (dq, J=8.7, 4.5 Hz, 1H), 4.10-4.02 (m, 1H), 4.00 (dd, J=9.1, 1.6 Hz, 1H), 3.31-3.21 (m, 2H), 3.09-3.02 (m, 1H), 3.01-2.91 (m; 2H), 2.88 (dt, J=9.1; 4.7 Hz, 1H), 2.80 (dt, J=16.2, 8.1 Hz, 1H), 2.77-2.69 (m, 1H), 1.90-1.83 (m, 1H), 1.74-1.54 (m, 6H), 1.45-1.35 (m, 1H), 1.19 (s, 9H), 1.07 (d, J=6.6 Hz, 3H), 1.00 (dd, J=6.6, 3.2 Hz, 3H), 0.96-0.89 (m, 3H), 0.87 (d, J=6.3 Hz, 3H); MW: 745.9 g/mol; LC-MS m/z: 746.4

Compound 32:

MW: 787.9 g/mol; LC-MS m/z: 788.5

Compound 33:

¹H NMR (700 MHz, DMSO-d₆) δ 8.83 (br s, 1H), 8.70 (d, J=7.5 Hz, 1H), 8.43 (d, J=6.3 Hz, 1H), 7.88 (s, 1H), 7.68 (d, J=10.2 Hz, 1H), 7.40 (d, J=10.0 Hz, 1H), 7.05 (d, J=8.5 Hz, 2H), 6.63 (d, J=8.5 Hz, 2H), 4.65 (td, J=11.1, 10.5, 3.8 Hz, 1H), 4.35 (td, J=8.1, 4.3 Hz, 1H), 4.17 (dd, J=10.1, 3.4 Hz, 1H), 4.14-4.10 (m, 1H), 4.08-4.03 (m, 1H), 3.99 (d, J=10.3 Hz, 1H), 3.86 (td, J=7.6, 2.7 Hz, 1H), 3.30-3.24 (m, 1H), 3.00-2.94 (m, 2H), 2.88-2.76 (m, 3H), 2.73-2.65 (m, 1H), 1.71-1.63 (m, 1H), 1.58 (dt, J=14.5, 7.5 Hz, 1H), 1.49 (ddd, J=14.4, 8.5, 4.4 Hz, 2H), 1.46-1.39 (m, 1H), 1.23 (s, 9H), 1.20 (d, J=6.9 Hz, 3H), 1.09 (dd, J=11.2, 5.2 Hz, 1H), 1.05 (d, J=6.4 Hz, 3H), 0.93 (d, J=6.5 Hz, 3H), 0.88 (d, J=6.6 Hz, 3H), 0.86-0.79 (m, 1H); MW: 745.9 g/mol; LC-MS m/z: 746.6

Compound 34:

¹H NMR (700 MHz, DMSO-d₆) δ 9.00 (br s, 1H), 7.58 (d, J=9.7 Hz, 1H), 7.53 (s, 1H), 7.05-6.96 (m, 3H), 6.94 (d, J=8.9 Hz, 1H), 6.73 (s, 1H), 6.68-6.58 (m, 2H), 4.49 (dt, J=9.7, 7.3 Hz, 1H), 4.29 (tt, J=7.0, 3.4 Hz, 1H), 4.26-4.18 (m, 2H), 4.10-4.02 (m, 1H), 3.98 (dd, J=9.0, 1.6 Hz, 1H), 3.28-3.21 (m, 2H), 3.06 (dd, J=8.6, 7.3 Hz, 1H), 2.96 (d, J=7.3 Hz, 2H), 2.91-2.85 (m, 1H), 2.78-2.70 (m, 1H), 2.66 (dd, J=17.1, 3.9 Hz, 1H), 1.87 (dq, J=12.3, 8.1 Hz, 1H), 1.72-1.61 (m, 3H), 1.62-1.54 (m, 2H), 1.41 (dddd, J=12.5, 8.6, 7.0, 5.5 Hz, 1H), 1.20 (s, 9H), 1.06 (d, J=6.5 Hz, 3H), 1.00 (d, J=6.4 Hz, 3H), 0.92 (d, J=6.3 Hz, 3H), 0.86 (d, J=6.4 Hz, 3H). ¹³C NMR (126 MHz, DMSO-d₆) δ 174.3, 173.4, 172.2, 171.8, 171.1, 169.8, 169.0, 156.4, 130.5, 127.9, 115.3, 65.9, 65.9, 64.4, 57.8, 54.4, 53.3, 51.8, 50.9, 46.5, 45.8, 41.4, 36.5, 35.8, 29.6, 28.5, 24.6, 23.8, 23.7, 21.4, 21.0, 19.2; MW: 745.9 g/mol; LC-MS m/z: 746.4

Compound 35:

MW: 745.9 g/mol; LC-MS m/z: 746.5

Compound 36:

Mixture of conformers, 1:1 ratio.

¹H NMR (500 MHz, DMSO-d₆) δ 8.94 (d, J=3.3 Hz, 1H), 8.71 (d, J=6.7 Hz, 1H), 8.52 (d, J=7.4 Hz, 1H), 8.29 (br s, 1H), 7.94 (d, J=6.9 Hz, 1H), 7.75 (d, J=10.4 Hz, 1H), 7.70 (d, J=9.7 Hz, 1H), 7.50 (d, J=10.0 Hz, 1H), 7.33-7.22 (m, 2H), 7.05-6.98 (m, 4H), 6.65-6.58 (m, 4H), 4.94 (br s, 1H), 4.85 (d, J=5.5 Hz, 1H), 4.63 (td, J=10.4, 5.0 Hz, 1H), 4.54 (td, J=10.3, 4.3 Hz, 1H), 4.37 (ddd, J=8.9, 7.2, 4.3 Hz, 1H), 4.30-4.23 (m, 2H), 4.16-4.08 (m, 2H), 4.09-4.01 (m, 2H), 3.97 (td, J=7.5, 4.2 Hz, 1H), 3.78 (tt, J=6.8, 3.2 Hz, 1H), 3.20-3.15 (m, 3H), 3.12-3.00 (m, 3H), 2.92-2.71 (m, 6H), 2.71-2.64 (m, 1H), 2.44 (t, J=11.9 Hz, 1H), 2.39-2.32 (m, 1H), 2.30-2.15 (m, 2H), 2.12-2.03 (m, 1H), 1.93-1.78 (m, 2H), 1.70-1.48 (m, 7H), 1.49-1.40 (m, 2H), 1.39-1.31 (m, 1H), 1.30-1.20 (m, 2H), 1.13 (d, J=6.8 Hz, 3H), 1.08-0.98 (m, 6H), 0.96 (d, J=6.6 Hz, 3H), 0.92-0.87 (m, 9H), 0.87-0.80 (m, 3H); MW: 646.7 g/mol; LC-MS m/z: 647.3

Compound 37:

¹H NMR (500 MHz, DMSO-d₆) δ 8.85 (br s, 1H), 8.78 (d, J=7.4 Hz, 1H), 8.55 (t, J=5.7 Hz, 1H), 7.74 (s, 1H), 7.64 (d, J=9.8 Hz, 1H), 7.59 (d, J=10.1 Hz, 1H), 7.06-7.00 (m, 2H), 6.67-6.62 (m, 2H), 4.80 (br s, 1H), 4.62-4.52 (m, 1H), 4.23 (ddd, J=10.2, 4.3, 2.4 Hz, 2H), 4.03 (dd, J=9.4, 1.6 Hz, 1H), 3.94-3.83 (m, 2H), 3.56 (dd, J=10.6, 2.8 Hz, 1H), 3.30-3.23 (m, 2H), 2.87 (dt, J=24.8, 8.4 Hz, 2H), 2.80-2.73 (m, 3H), 2.69-2.59 (m, 1H), 1.66 (dt, J=13.3, 6.6 Hz, 1H), 1.61-1.47 (m, 4H), 1.43 (t, J=5.9 Hz, 1H), 1.23 (s, 9H), 1.06 (d, J=6.3 Hz, 3H), 1.01 (t, J=3.2 Hz, 1H), 0.94 (d, J=6.5 Hz, 3H), 0.88 (d, J=6.5 Hz, 3H); MW: 731.8 g/mol; LC-MS m/z: 732.4

Compound 38:

¹H NMR (500 MHz, DMSO-d₆) δ 8.92 (br s, 1H), 8.76 (br s, 1H), 7.88 (d, J=10.5 Hz, 1H), 7.68 (d, J=7.7 Hz, 1H), 7.54 (s, 1H), 7.35 (d, J=9.9 Hz, 1H), 7.05 (d, J=8.5 Hz, 2H), 6.61 (d, J=8.5 Hz, 2H), 5.08 (br s, 1H), 4.60 (td, J=11.0, 4.1 Hz, 1H), 4.29 (q, J=6.3 Hz, 1H), 4.24 (dd, J=10.0, 3.1 Hz, 1H), 4.07-4.00 (m, 1H), 3.92 (dd, J=12.0, 8.5 Hz, 1H), 3.87 (ddd, J=9.0, 5.9, 3.1 Hz, 1H), 3.41-3.36 (m, 1H), 3.19-3.08 (m, 2H), 3.05 (dd, J=9.8, 4.3 Hz, 1H), 2.96 (d, J=13.2 Hz, 1H), 2.92-2.82 (m, 2H), 2.70-2.61 (m, 1H), 2.50-2.42 (m, 1H), 1.87-1.76 (m, 1H), 1.71 (dq, J=13.1, 6.6 Hz, 1H), 1.66-1.57 (m, 2H), 1.50 (ddd, J=14.1, 8.2, 5.9 Hz, 2H), 1.34-1.26 (m, 1H), 1.21 (s, 9H), 1.03 (d, J=6.4 Hz, 3H), 0.94 (d, J=6.5 Hz, 3H), 0.88 (d, J=6.5 Hz, 3H); MW: 731.8 g/mol; LC-MS m/z: 732.4

Compound 39:

¹H NMR (500 MHz, DMSO-d₆) δ 8.78 (d, J=3.2 Hz, 1H), 8.58 (d, J=7.1 Hz, 1H), 7.81 (d, J=10.3 Hz, 1H), 7.72 (dd, J=7.4, 3.3 Hz, 1H), 7.43 (d, J=9.9 Hz, 1H), 7.30-7.22 (m, 4H), 7.22-7.12 (m, 1H), 4.99 (d, J=4.7 Hz, 1H), 4.69 (ddd, J=11.6, 10.3, 4.1 Hz, 1H), 4.33 (ddd, J=9.5, 7.1, 4.1 Hz, 1H), 4.29-4.22 (m, 1H), 4.13-4.04 (m, 1H), 3.88 (td, J=7.5, 3.2 Hz, 1H), 3.65 (dtd, J=12.4, 6.8, 2.5 Hz, 1H), 3.29 (dd, J=13.9, 4.1 Hz, 1H), 3.11 (ddd, J=8.6, 6.9, 1.8 Hz, 1H), 2.94-2.77 (m, 4H), 2.72 (dd, J=9.8, 5.4 Hz, 1H), 2.67-2.59 (m, 1H), 2.48-2.41 (m, 1H), 2.16-2.08 (m, 1H), 1.88-1.77 (m, 1H), 1.68-1.42 (m, 5H), 1.26-1.14 (m, 1H), 1.03 (d, J=6.4 Hz, 3H), 0.92 (d, J=6.3 Hz, 3H), 0.88 (d, J=6.4 Hz, 3H); MW: 616.7 g/mol; LC-MS m/z: 617.3

Compound 40:

1H NMR (700 MHz, DMSO-ds) b 9.02 (d, J=4.2 Hz, 1H), 8.43 (d, J=7.6 Hz, 1H), 7.46 (d, J=7.5 Hz, 1H), 7.03-6.97 (m, 2H), 6.82 (d, J=8.7 Hz, 1H), 6.75 (s, 1H), 6.69 (br s, 1H), 6.65-6.60 (m, 2H), 5.02 (s, 1H), 4.49 (q, J=7.5 Hz, 1H), 4.32-4.23 (m, 2H), 4.18 (td, J=6.4, 4.2 Hz, 1H), 4.04-3.94 (m, 1H), 3.88 (dd, J=8.7, 1.9 Hz, 1H), 3.34-3.28 (m, 1H), 3.11 (d, J=9.9 Hz, 1H), 3.01 (dd, J=14.4, 6.4 Hz, 1H), 2.89 (q, J=8.2 Hz, 1H), 2.80-2.68 (m, 4H), 1.77-1.69 (m, 1H), 1.69-1.58 (m, 4H), 1.53 (dtd, J=11.9, 9.2, 8.1, 6.0 Hz, 1H), 1.40 (dd, J=11.6, 9.5 Hz, 1H), 1.25 (s, 9H), 0.98 (dd, J=17.0, 6.5 Hz, 6H), 0.85 (dd, J=10.9, 6.0 Hz, 6H). ¹³C NMR (126 MHz, DMSO-d₆) δ 175.1, 174.9, 171.7, 171.4, 170.6, 169.2, 168.7, 156.1, 130.2; 128.6, 115.3, 65.5, 64.9, 64.6, 58.2, 53.9, 53.3, 51.0, 50.8, 45.7, 41.2, 40.9, 35.5, 34.0, 28.7, 28.6, 24.8, 24.0, 23.7, 21.3, 20.9, 19.2; MW: 745.9 g/mol; LC-MS m/z: 746.4

Compound 41:

1H NMR (500 MHz, DMSO-d6) δ 9.15 (br s, 1H), 8.43 (d, J=7.6 Hz, 1H), 7.54-7.44 (m, 1H), 7.08-6.97 (m, 2H), 6.92 (d, J=8.6 Hz, 1H), 6.76 (br s, 2H), 6.68-6.57 (m, 2H), 4.49 (q, J=7.6 Hz, 1H), 4.28 (tt, J=7.2, 4.2 Hz, 2H), 4.17 (d, J=4.9 Hz, 1H), 4.04-3.92 (m, 1H), 3.86 (dd, J=8.6, 2.0 Hz, 1H), 3.37-3.26 (m, 1H), 3.10 (d, J=9.9 Hz, 1H), 3.01 (dd, J=14.3, 6.2 Hz, 1H), 2.93 (q, J=8.1 Hz, 1H), 2.80-2.69 (m, 2H), 2.60 (d, J=7.2 Hz, 2H), 1.78-1.67 (m, 1H), 1.68-1.56 (m, 4H), 1.55-1.46 (m, 1H), 1.39 (dd, J=12.5, 9.9 Hz, 1H), 1.25 (s, 9H), 0.98 (dd, J=15.1, 6.4 Hz, 6H), 0.85 (dd, J=10.2, 6.2 Hz, 6H); MW: 745.9 g/mol; LC-MS m/z: 746.4

Compound 42:

¹H NMR (500 MHz, DMSO-d₆) δ 8.69-8.60 (m, 1H), 8.50-8.39 (m, 1H), 8.13-8.06 (m, 1H), 7.79 (s, 1H), 7.45 (d, J=8.4 Hz, 1H), 7.35-7.26 (m, 1H), 7.01-6.89 (m, 2H), 6.62 (d, J=8.5 Hz, 2H), 4.80 (s, 1H), 4.40 (dt, J=8.2, 6.9 Hz, 1H), 4.27 (q, J=7.4 Hz, 1H), 4.17 (dd, J=9.0, 2.7 Hz, 1H), 3.95 (s, 1H), 3.90-3.79 (m, 2H), 3.67-3.56 (m, 1H), 3.50 (d, J=10.1 Hz, 1H), 2.97 (q, J=7.2, 4.9 Hz, 1H), 2.92-2.84 (m, 2H), 2.80 (t, J=6.6 Hz, 3H), 1.70 (dt, J=11.7, 8.8 Hz, 1H), 1.65-1.51 (m, 2H), 1.39 (td, J=15.2, 14.0, 7.4 Hz, 4H), 1.25 (s, 10H), 1.11 (d, J=6.4 Hz, 3H), 0.98 (d, J=6.3 Hz, 3H), 0.83 (d, J=5.8 Hz, 3H), 0.72 (d, J=5.4 Hz, 3H); MW: 745.9 g/mol; LC-MS m/z: 746.4

Compound 43:

MW: 787.9 g/mol; LC-MS m/z: 788.5

Compound 44:

¹H NMR (700 MHz, DMSO-d₆) δ 9.20 (s, 1H), 8.65 (d, J=4.5 Hz, 1H), 7.65 (d, J=6.6 Hz, 1H), 6.95-6.91 (m, 2H), 6.88 (d, J=9.0 Hz, 1H), 6.84 (dd, J=9.0, 7.5 Hz, 2H), 6.69-6.65 (m, 2H), 6.28 (s, 1H), 5.01 (s, 1H), 4.33-4.26 (m, 2H), 4.24 (dt, J=8.6, 4.3 Hz, 1H), 4.18-4.13 (m, 1H), 4.07-3.99 (m, 1H), 3.90 (dd, J=9.1, 1.6 Hz, 1H), 3.39 (q, J=8.0 Hz, 1H), 3.22 (d, J=10.7 Hz, 1H), 3.11 (dd, J=9.2, 5.8 Hz, 1H), 2.82 (ddd, J=10.4, 6.9, 2.3 Hz, 1H), 2.79-2.68 (m, 2H), 2.67-2.56 (m, 1H), 2.33-2.22 (m, 1H), 2.02-1.92 (m, 1H), 1.76-1.60 (m, 3H), 1.59-1.50 (m, 2H), 1.20 (s, 9H), 1.08 (d, J=6.5 Hz, 3H), 1.00 (d, J=6.5 Hz, 3H), 0.89 (d, J=6.6 Hz, 3H), 0.85 (d, J=6.5 Hz, 3H); MW: 759.9 g/mol; LC-MS m/z: 760.4

Compound 45:

MW: 759.9 g/mol; LC-MS m/z: 760.4

Compound 46:

MW: 693.8 g/mol; LC-MS m/z: 694.4

Compound 47:

MW: 773.9 g/mol; LC-MS m/z: 774.4

Compound 48:

¹H NMR (500 MHz, DMSO-d₆) δ 9.21 (br s, 1H), 7.95-7.82 (m, 2H), 6.99-6.91 (m, 2H), 6.88 (d, J=9.6 Hz, 1H), 6.80 (s, 1H), 6.71-6.59 (m, 3H), 5.18-5.07 (m, 1H), 4.80 (q, J=7.8 Hz, 1H), 4.73-4.63 (m, 1H), 4.56-4.50 (m, 1H), 4.38-4.28 (m, 2H), 4.28-4.20 (m, 1H), 3.82 (dd, J=9.0, 1.3 Hz, 1H), 3.35-3.32 (m, 2H), 3.03-2.58 (m, 7H), 2.25 (d, J=11.3 Hz, 1H), 1.91-1.79 (m, 1H), 1.72-1.44 (m, 10H), 1.28 (td, J=7.0, 0.8 Hz, 3H), 1.20 (s, 9H), 1.01 (d, J=6.4 Hz, 3H), 0.88 (dd, J=14.2, 6.5 Hz, 6H); MW: 843.0 g/mol; LC-MS m/z: 843.6

Compound 49:

MW: 843.0 g/mol; LC-MS m/z: 843.4

Compound 50:

MW: 816.9 g/mol; LC-MS m/z: 817.4

Compound 51:

MW: 816.9 g/mol; LC-MS m/z: 817.4

Compound 52:

¹H NMR (700 MHz, DMSO-d₆) δ 8.95 (d, J=5.2 Hz, 1H), 8.21-8.15 (m, 1H), 8.02 (d, J=7.5 Hz, 1H), 7.65 (dd, J=7.4, 1.4 Hz, 2H), 7.46-7.43 (m, 1H), 7.40 (td, J=7.5, 0.9 Hz, 1H), 7.04 (s, 1H), 7.01 (d, J=9.3 Hz, 1H), 6.90 (d, J=9.1 Hz, 1H), 5.01 (s, 1H), 4.69-4.56 (m, 2H), 4.35 (dt, J=6.8, 5.6 Hz, 1H), 4.32-4.28 (m, 1H), 4.26-4.18 (m, 1H), 4.15 (dd, J=15.8, 5.2 Hz, 1H), 3.95 (dd, J=9.2, 1.8 Hz, 1H), 3.58-3.49 (m, 2H), 3.35-3.28 (m, 1H), 3.22 (d, J=10.6 Hz, 1H), 2.92 (ddd, J=8.9, 6.7, 2.6 Hz, 1H), 2.76 (d, J=6.3 Hz, 2H), 1.87 (tdd, J=12.6, 9.9, 7.0 Hz, 1H), 1.75-1.66 (m, 4H), 1.61 (qt, J=12.2, 10.7, 4.1 Hz, 2H), 1.26 (d, J=6.5 Hz, 3H), 1.20 (s, 9H), 0.99 (d, J=6.4 Hz, 3H), 0.94 (d, J=6.4 Hz, 3H), 0.86 (d, J=6.4 Hz, 3H); MW: 715.8 g/mol; LC-MS m/z: 716.3

Compound 53:

¹H NMR (700 MHz, DMSO-d₆) δ 12.54 (s, 1H), 8.95 (d, J=5.2 Hz, 1H), 8.73-8.65 (m, 2H), 8.18 (t, J=6.5 Hz, 1H), 8.17-8.11 (m, 1H), 7.84-7.74 (m, 2H), 7.50-7.43 (m, 2H), 7.37 (d, J=7.8 Hz, 1H), 7.01 (s, 1H), 6.98 (d, J=9.3 Hz, 1H), 6.92 (d, J=9.1 Hz, 1H), 5.03 (d, J=4.5 Hz, 1H), 4.62 (ddd, J=11.3, 7.2, 3.7 Hz, 1H), 4.51 (dd, J=15.8, 7.3 Hz, 1H), 4.42-4.35 (m, 1H), 4.30 (ddd, J=6.5, 4.5, 1.7 Hz, 1H), 4.22 (ddd, J=10.7, 9.4, 6.5 Hz, 1H), 4.11 (dd, J=15.9, 5.5 Hz, 1H), 3.96 (dd, J=9.2, 1.7 Hz, 1H), 3.57-3.50 (m, 2H), 3.25 (d, J=10.6 Hz, 1H), 2.91 (ddd, J=8.9, 6.7, 2.5 Hz, 1H), 2.78 (d, J=6.3 Hz, 2H), 1.83 (ddt, J=9.8, 5.4, 2.3 Hz, 1H), 1.78-1.70 (m, 2H), 1.70-1.60 (m, 3H), 1.54 (dddd, J=15.8, 11.4, 6.0, 4.0 Hz, 1H), 1.29 (d, J=6.5 Hz, 3H), 1.21 (s, 9H), 0.98 (d, J=6.4 Hz, 3H), 0.95 (d, J=6.5 Hz, 3H), 0.88 (d, J=6.5 Hz, 3H). ¹³C NMR (126 MHz, DMSO-d₆) δ 175.01, 174.93, 171.83, 170.18, 169.86, 169.03, 167.29, 150.18, 147.53, 140.74, 137.41, 134.85, 129.82, 126.64, 126.35, 124.45, 67.57, 65.63, 64.91, 57.77, 52.59, 51.95, 50.87, 46.53, 45.44, 41.67, 35.66, 31.20, 28.65, 24.82, 24.69, 23.76, 21.40, 20.86, 20.47; MW: 792.9 g/mol; LC-MS m/z: 793.4

Compound 54:

MW: 888.1 g/mol; LC-MS m/z: 888.4

Compound 55:

MW: 871.0 g/mol; LC-MS m/z: 871.5

Compound 56:

MW: 857.0 g/mol; LC-MS m/z: 857.4

Compound 57:

¹H NMR (500 MHz, DMSO-d₆) δ 9.36 (br s, 1H), 8.84-8.66 (m, 1H), 8.44 (d, J=6.5 Hz, 1H), 7.59-7.35 (m, 2H), 7.02-6.87 (m, 2H), 6.89-6.83 (m, 1H), 6.68-6.60 (m, 2H), 6.62-6.54 (m, 2H), 5.16 (br s, 1H), 4.56-4.48 (m, 1H), 4.44 (q, J=7.1 Hz, 1H), 4.35-4.24 (m, 2H), 4.11-4.02 (m, 1H), 3.92-3.77 (m, 2H), 3.48 (d, J=7.8 Hz, 1H), 3.39 (d, J=5.4 Hz, 1H), 3.25 (dd, J=9.6, 3.0 Hz, 1H), 3.02 (d, J=10.8 Hz, 1H), 2.90 (dd, J=13.9, 5.3 Hz, 1H), 2.72 (t, J=7.6 Hz, 1H), 2.69-2.59 (m, 3H), 1.79 (dq, J=16.3, 11.0, 10.5 Hz, 2H), 1.74-1.62 (m, 1H), 1.63-1.47 (m, 3H), 1.39-1.29 (m, 1H), 1.26 (d, J=7.0 Hz, 3H), 1.21 (s, 9H), 1.12 (d, J=6.4 Hz, 3H), 1.03 (d, J=6.4 Hz, 3H), 0.84 (dd, J=6.6, 2.1 Hz, 6H); MW: 874.0 g/mol; LC-MS m/z: 874.4

Compound 58:

MW: 772.9 g/mol; LC-MS m/z: 773.5

Although preferred embodiments of the invention have been described herein, it will be understood by those skilled in the art that variations may be made thereto without departing from the spirit of the invention or the scope of the appended claims. All documents disclosed herein, including those in the following reference list, are incorporated by reference. 

The invention claimed is:
 1. A process for preparing a cyclic peptide of formula (II):

wherein: —C(O)-L-Z— is selected from the group consisting of:

comprising the following steps: (i) cyclizing head-to-tail a linear peptide of formula (IIa):

wherein: R^(d) is tert-butyloxycarbonyl or 9-fluorenylmethoxycarbonyl; and —C(O)-L-Z′ is selected from the group consisting of:

in the presence of 3-(diethoxyphosphoryloxy)-1,2,3-benzotriazin-4(3H)-one, to provide a cyclic peptide of formula (IIb):

wherein: R^(d) is tert-butyloxycarbonyl or 9-fluorenylmethoxycarbonyl; and —C(O)-L-Z— is selected from the group consisting of:

(ii) deprotecting the cyclic peptide of formula (IIb) above in the presence of piperidine and N-methyl-2-pyrrolidone, to provide the cyclic peptide of formula (II) above.
 2. The process of claim 1, wherein —C(O)-L-Z— is:


3. The process of claim 1, wherein —C(O)-L-Z— is:


4. The process of claim 1, wherein —C(O)-L-Z— is:


5. The process of claim 1, wherein —C(O)-L-Z— is:


6. The process of claim 1, wherein —C(O)-L-Z— is: 